Traditional petrochemical-based plastics are formulated to be strong, lightweight, and durable. However, these plastics are typically not biodegradable, and as a result, hundreds of millions of tons of plastic sits in landfills or floats in the ocean.
Petrochemical-based plastic materials, such as large quantities of polyethylene and polypropylene, as well as numerous other plastics (polyethylene terephthalate, polyester, polystyrene, ABS, polyvinyl chloride, polycarbonate, nylon, and the like) are typically not readily biodegradable, nor are such materials typically sourced from renewable sources.
Recently efforts have been made to reduce the use of such non-renewable petrochemical-based plastic materials. Some such efforts have attempted to source resins for producing plastic materials from renewable sources, such as from sugarcane or other plant products. While available to some degree, such renewable sourced plastics have been far more expensive to produce than their petrochemical-based non-renewable counterparts.
In addition, plastic materials have particular strength characteristics associated therewith, dependent on the particular material(s) employed in forming the plastic film or other material, and physical characteristics of the film or other article itself. For example, when forming a plastic film, use of the non-renewable petrochemical-based plastic resin material can be reduced by forming a thinner film, but such reductions in material use result in a weaker film.
By way of example, while WO 2014/0190395 to Leufgens describes formation of films from a blend of polyethylene and a thermoplastic starch (particularly Cardia BL-F), such films are weaker than comparable films formed from the polyethylene alone, and because of the difficulties in processing blends including conventional thermoplastic starches, the films produced therein are of necessity very thick (e.g., 3 mils). Such very thick films may not result in any actual reduction in the use of the petrochemical based plastic resin material, because thin film formation is impossible as a practical matter, and/or because the inclusion of such thermoplastic starches weakens the overall film, so that a thick film is needed to maintain a desired level of strength.
It would be advantageous to provide films and associated methods of manufacture that might increase strength for any given film thickness, e.g., by adjusting the manufacturing parameters employed during manufacture, when using a renewable sourced plastic material. Such methods would allow a film to be produced at a given thickness with increased strength, or to produce the film at a lower thickness, but with the same strength. Such methods at the same time would result in actual reductions in the quantity of petrochemical plastic material employed, as a portion thereof is substituted with a renewable sourced plastic material, and the overall thickness does not need to be increased.